It is known of internal combustion engines with single injection to suppress the fuel supply to one cylinder by switching off the injection valve as soon as it is found that this cylinder has failed, that is to say, a state has occurred in which reliable combustion is no longer possible. The remaining cylinders are still operated in unchanged manner, that is to say, as if all cylinders were still satisfactorily operating.
In internal combustion engines with single injection, it is obviously possible in a very simple manner to reduce the fuel supply to a selected cylinder down to the amount of zero. For internal combustion engines with centralized injection, in contrast, hitherto only methods have been known which permit a reduction of the fuel supply for a selected cylinder only in a small ratio with respect to the fuel quantity supplied to the other cylinders. A method for reducing the fuel supply for a selected cylinder of a multi-cylinder internal combustion engine with centralized injection is known from DE 2,929,516 C2. The beginning and length of operation of the fuel injection valve can be individually determined for each individual cylinder. The values are selected in such a manner that optimum operation of the internal combustion engine is achieved. Using the known method, it is not possible to reduce the fuel quantity for a single cylinder in this manner to such a low value as is required when the cylinder has failed. Accordingly, there is not even an investigation as to whether a cylinder has failed in the known method.
The great reduction of fuel supplied to a failed cylinder is required since, in the motor vehicles with catalytic converter, which have been produced in large volumes for some time, it is dangerous to send unburnt fuel into the catalytic converter. This is because fuel is subjected there to post-combustion, which can lead to overheating of the catalytic converter when the fuel quantity is too large, and thus to the hazard of a fire for the entire vehicle.
For some time, there has therefore been a need to find a method enabling a failed cylinder to be supplied with only extremely little fuel, for internal combustion engines with centralized injection, the internal combustion engine, however, still remaining operable so that the vehicle with the defective internal combustion engine does not remain stopped. In vehicles with catalytic converters, the internal combustion engine previously had to be switched off when a cylinder failed in order to prevent, by this switching-off, an overheating of the catalytic converter.